The present invention disclosed herein relates to a transmitter, and more particularly, to a transmitter oscillating to output a digital signal through an oscillation circuit.
A transmitter requires an oscillation circuit oscillating a digital signal at a high frequency and modulating the digital signal using an oscillation signal in a type required by a system. The oscillation circuit is required to oscillate a digital signal at least 5 times or greater and output the oscillated digital signal. Then, when the modulated output signal is smaller, the transmitter may include a power amplifier at a following stage.
A digital signal modulation method of an oscillation circuit include a modulation method by a manual switch, a modulation method using an amplifier, and a modulation method in an oscillation circuit itself. For a case of using an amplifier, it is difficult to implement a low power transmitter due to additional power consumption. For the modulation method through a manual switch, a large loss is caused by manual devices. In addition, an effect by parasitic components is great.
The modulation method in an oscillating circuit itself does not oscillate when a digital signal is ‘0’ and starts to oscillate when the digital signal is ‘1’. At this point, the oscillation circuit has a minute output signal at initial oscillation, outputs a signal having gradually increased amplitude and finally outputs a signal having a saturated amplitude. However, in the modulation method by an oscillating circuit itself, an oscillation response speed may be slowed during a high speed operation.